go/zodb: Try to support bytes for OID

Since ZODB 5.4 OID is encoded as bytes, not str:

	https://github.com/zopefoundation/ZODB/commit/12ee41c473

Try to support both str and bytes on decoding, as we need to support all
ZODB versions.

go/zodb/internal/pickletools/pickletools.go

-// Copyright (C) 2017  Nexedi SA and Contributors.
-//                     Kirill Smelkov <kirr@nexedi.com>
+// Copyright (C) 2017-2019  Nexedi SA and Contributors.
+//                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This program is free software: you can Use, Study, Modify and Redistribute
 // it under the terms of the GNU General Public License version 3, or (at your
@@ -23,7 +23,11 @@
 package pickletools
 
 import (
+	"encoding/binary"
+	"fmt"
 	"math/big"
+
+	pickle "github.com/kisielk/og-rek"
 )
 
 // Xint64 tries to convert unpickled value to int64.
@@ -41,3 +45,34 @@ func Xint64(xv interface{}) (v int64, ok bool) {
 
 	return 0, false
 }
+
+// Xstrbytes verifies and extacts str|bytes from unpickled value.
+func Xstrbytes(x interface{}) (string, error) {
+	var s string
+	switch x := x.(type) {
+	default:
+		return "", fmt.Errorf("expect str|bytes; got %T", x)
+
+	case string:
+		s = x
+
+	case pickle.Bytes:
+		s = string(x)
+	}
+
+	return s, nil
+}
+
+// Xstrbytes8 verifies and extracts [8](str|bytes) from unpickled value as big-endian u64.
+func Xstrbytes8(x interface{}) (uint64, error) {
+	s, err := Xstrbytes(x)
+	if err != nil {
+		return 0, err
+	}
+
+	if len(s) != 8 {
+		return 0, fmt.Errorf("expect [8]bytes; got [%d]bytes", len(s))
+	}
+
+	return binary.BigEndian.Uint64([]byte(s)), nil
+}

go/zodb/pydata.go

@@ -22,11 +22,12 @@ package zodb
 
 import (
 	"bytes"
-	"encoding/binary"
 	"fmt"
 	"strings"
 
 	pickle "github.com/kisielk/og-rek"
+	"lab.nexedi.com/kirr/neo/go/zodb/internal/pickletools"
+
 	"lab.nexedi.com/kirr/go123/xerr"
 )
 
@@ -232,20 +233,17 @@ func xpyclass(xklass interface{}) (_ pickle.Class, err error) {
 }
 
 // xoid verifies and extracts oid from unpickled value.
-//
-// TODO +zobdpickle.binary support
 func xoid(x interface{}) (_ Oid, err error) {
 	defer xerr.Context(&err, "oid")
 
-	s, ok := x.(string)
-	if !ok {
-		return InvalidOid, fmt.Errorf("expect str; got %T", x)
-	}
-	if len(s) != 8 {
-		return InvalidOid, fmt.Errorf("expect [8]str; got [%d]str", len(s))
+	// ZODB >= 5.4 encodes oid as bytes; before - as str:
+	// https://github.com/zopefoundation/ZODB/commit/12ee41c473
+	v, err := pickletools.Xstrbytes8(x)
+	if err != nil {
+		return InvalidOid, err
 	}
 
-	return Oid(binary.BigEndian.Uint64([]byte(s))), nil
+	return Oid(v), nil
 }
 
 // pyclassPath returns full path for a python class.